Patent GB-836418-A (GB)
Title: Improvements in and relating to thermostatic control systems for liquid fuel burners
Inventor: HASLEHURST ARTHUR KINDER
IPC: G05D23/08
Filed: 1956-06-27
Abstract: 836,418. Controlling liquid fuel supply to burners. PARAMATIC DEVELOPMENT Ltd. June 27, 1957 [June 27, 1956; July 13, 1956], Nos. 19826/56 and 21654/56. Class 75(1) [Also in Group XXIX] Liquid fuel for a burner heating a chamber or container such as a water tank, a hot-air chamber such as an oven or cooking stove or the primary chamber of an absorption type refrigerator, is controlled by each of two portions of a thermostatic system, for example, comprising two thermostats mechanically operatively associated with valve means for metering the supply of fuel to the burner one portion being responsive to the temperature of the water &c. and the other portion to the temperature of the burner chamber or fire-box both portions tending to reduce the fuel supply to the burner on heating. The two thermostats may operate upon the same or separate valves. As shown, the fuel valve 39 is operated by the thermostat in the form of a bimetallic strip 27-28 extending across the upper part of the burner chamber or fire box 35 of the burner 36. The water thermostat is a rod 13 having a low coefficient of expansion enclosed in a vertical tube 12 forming part of the water tank 10 having a relatively high co-efficient of expansion. The upper end of the rod has thereon an adjustable threaded nut 19, the rod being pressed downwardly by a spring 16 located between a cap 17 fixed on the end of the tube and a shoulder 15 on the rod, a gap 20 adjustable by the nut 19 being left between the cap 17 and the nut 19 so that the tank and tube have to expand before the cap 17 closes up this gap. The lower end of the rod 13 passes through the tank 10 into a hole 26 in a lug 25 secured to the bottom of the tank to bear upon the bimetallic strip 27, 28 fulcrumed at 29. The valve rod 41 is coupled mechanically to the end of the arm 27, 28, the valve tending to move under gravity to its closed position. In the unlighted condition of the burner the arm 27, 28 is undistorted and is pressed at the end opposite to the valve against an adjustable stop 50 by the rod 13 and in this position the valve is fully open as determined by the stop 50. As the temperature in the fire-box rises, the arm 27, 28 bends and the parts are adjusted to provide a maximum height of flame which is maintained while the water temperature rises and when the gap 20 has been closed the rod 13 is withdrawn upwardly from the arm, which moves on its pivot 29 allowing the fuel valve 39 to move towards its closed position by an amount determined by an adjustable stop 49 which fixes the minimum flame level. The stop 49 could be omitted and the valve would move to its closed position when the water temperature ceases to rise, the height of the flame being then adjusted to make good just the heat losses. In a modification the rod 13 acts on a rocker arm fulcrumed at one end with the arm 27, 28 attached at the other end. The bimetallic arm or the rocker arm may be rigidly attached to the end of the rod 13 to move bodily with it. In other modifications the movements of the thermostats may be integrated and the combined effect communicated to the valve mechanism by having two separate valves on the same flow line each operated by one thermostat (Figs. 4 and 5, not shown) or by having a single valve operated by the integrated movements of the two thermostats (Fig. 6 not shown).